Ouch! That's very disappointing news though I guess I can see why it might be costly to repair after factoring in labour, parts and shipping. But, for a prime lens ("prime" in the sense of being one of the best) announced only three years ago, it's a shame that Pentax don't offer that the failure was down to a manufacturing defect and make a suitable adjustment to the cost of repair.

Thank you for your post. Actually, Pentax no longer deals directly with customers for after-sales service. Customers should pass through retailers.

The SDM motor failure is mentioned in various forums, with some pentaxians being very vocal. Compiling the feed-back, SDM lenses seem to be very sensitive to 'impact damage'. Since I take great care of my gear, I'm surprised (understatement) .

I purchased one of the first lens available in France. Maybe quality wasn't on top.

Before being inert, my DA* 50-135 did a stuck focusing. In that case, the SDM motor was moving the AF painfully and slowly, as if the motor weren't powerful enough

My other SDM lenses, the 2 years old 16-50 and the 6 months old 60-250, both work perfectly and the ultrasonic motor is a true delight, fast and quiet. The 50-135 is the only one featuring internal zoom.

Anyway, I'm waiting for my lens and I hope I'll receive it soon before Spring

I would put very little stock in what you read on the internet. If go by what the Pentax forums say then:
1) SDM lenses are total failures.
2) Pentax cameras cannot autofocus.
3) The K-7 doesn't work in low light.
4) Pentax is doomed.